Do you have to plant more in the high-productivity zone?

Reading time: 10 min
The results of a huge experiment testing;nbsp: 6 hybrids in Ukraine
Experiment testing 6 corn hybrids_OneSoil Blog
"You have to plant more in the high-productivity zone." Variable-rate seeding for newbies most often starts off with this approach. To test whether this approach is grounded in fact, we teamed up with a Ukrainian agricultural holding in 2020 to conduct a huge experiment testing 6 hybrids in different soil types and climate zones. We lay out the results in the article.

The experiment was conducted in 19 fields covering a total of 2,270 hectares in several regions of Ukraine. The soil and climatic conditions differed across all fields. There were primarily chernozems in terms of soil types. Sod-podzolic soils were less common. The soil texture also varied, ranging from sand to loam. The amount of precipitation and the growing degree-days also changed in all regions.
Usevalad Henin
Usevalad is an expert in GIS and agricultural chemistry. He has been developing precision farming tools since 2013. He is also the co-founder of OneSoil.
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Philip Kondratenko_OneSoil Agronomist
Usevalad Henin
Usevalad is an expert in GIS and agricultural chemistry. He has been developing precision farming tools since 2013. He is also the co-founder of OneSoil.
"You have to plant more in the high-productivity zone." Variable-rate seeding for newbies most often starts off with this approach. To test whether this approach is grounded in fact, we teamed up with a Ukrainian agricultural holding in 2020 to conduct a huge experiment testing 6 hybrids in different soil types and climate zones. We lay out the results in the article.

The experiment was conducted in 19 fields covering a total of 2,270 hectares in several regions of Ukraine. The soil and climatic conditions differed across all fields. There were primarily chernozems in terms of soil types. Sod-podzolic soils were less common. The soil texture also varied, ranging from sand to loam. The amount of precipitation and the growing degree-days also changed in all regions.

Hybrids

For the experiment, we chose 6 hybrids that the agricultural holding used in the 2020 season: DKC 3939, DKC 4590, DKC 3972, DKC 4351, P 9241, and DKC 4541.

Seeding strategy

As I wrote above, in this field experiment, we tested whether the corn yield would increase if the seeding rate was increased in the high-productivity zone and decreased in the low-productivity zone. To this end, two additional controls were added to each field:
  1. For the first control, we decreased the seeding rate in the high-productivity zone and increased it in the low-productivity zone.
  2. For the second, the medium seeding rate was used in all productivity zones.

The medium seeding rate in this experiment was the agricultural holding's standard rate: 74,000 - 78,000 grains/ha. The other rates were selected based on the hybrid: the low rate was 65,000-69,000 per hectare, and the high rate was 80,000-87,000 per hectare.

I'd like to emphasize that, in order to receive objective results for the experiment, it was important to apply both controls in the same field. If you compare test strips from several fields, the result is unreliable due to different planting dates and applications of plant protection products, growth regulators, etc.

Experimental setup

Examine at least three years of NDVI data. I start every field experiment by doing this. NDVI data in a field correlates with yield in key growth stages. That's why I can identify productivity zones and understand how stable they are when I rely on several years of NDVI data.

You can view NDVI data for any day for free in the OneSoil web app.
To see what the vegetation zones in a field looked like on any given day over the past 3-4 years, check out the OneSoil web app. You'll have to spend a little time, but it's well worth it
Identify the nature of the productivity zones to determine if they are stable or unstable. If the NDVI zones in the field change from year to year, it means that the zones are unstable. The yield in a field like this is primarily limited by external environmental factors, such as the weather. If the zones' locations are stable from season to season, yield is primarily affected by an internal factor. In fields like these, it's easier to delimit zones for seeding and forecast the result. These are the kinds of fields I select for experiments.

Create a prescription map. At this stage, I allocate the seeding rates across the field so that I end up with three seeding rates in each productivity zone. It looks something like this:

Analyze the results after harvest. It's important to harvest all the fields where experiments were held with a combine equipped with yield monitoring. Otherwise, you won't be able to correctly interpret the experiment results. After I get a yield map, I manually delimit replications on it. These are areas that have the same yield and seeding rate values in a particular productivity zone. To get the experiment results, I compare the average yield for the replications in different zones.

Experiment findings

DKC 3939 (FAO 320). In fields that didn't get enough moisture, the yield increased in low-productivity areas with a lower seeding rate. In the fields that didn't see any drought conditions, the yield increased in high-productivity zones with a higher seeding rate and often in low-productivity zones with a lower seeding rate.
The results for hybrid DKC 3939 on a field with moisture issues_OneSoil Blog
The results in a field where the hybrid DKC 3939 was used for the experiment and there were issues with moisture Yield, t/ha
The results for hybrid DKC 3939 on a field without moisture issues_OneSoil Blog
The results in a field where the hybrid DKC 3939 was used for the experiment and that didn't have any moisture issues Yield, t/ha
DKC 3972 (FAO 300). In high-productivity zones, yield increased when raising the seeding rate to 87,000 seeds per hectare and in low-productivity zones when lowering the seeding rate to 68,000 seeds per hectare. The average yield growth when changing the seeding rate was 1.1 t/ha.
he results for hybrid DKC 3972_OneSoil Blog
The results in a field where the hybrid DKC 3972 was used for the experiment
DKC 4351 (FAO 350). This hybrid is unstable. In some fields, the yield increased when increasing the seeding rate in high-productivity zones. In others, the yield grew in both low- and high-productivity zones when decreasing the seeding rate. To understand why this happened and whether this hybrid had a dependence on any factors, we had to continue experimenting. For this hybrid, I've decided to show charts for two fields to give the whole picture.
The results for hybrid DKC 4351, 1st field_OneSoil Blog
The results in the first field, where I tested the hybrid DKC 4351
The results for hybrid DKC 4351, 2nd field_OneSoil Blog
The results in the second field, where I tested the hybrid DKC 4351
DKC 4590 (FAO 360), P 9241 (FAO 340), DKC 4541 (FAO 360). The yield for these three hybrids in different fields and in different conditions didn't depend on the seeding rate. That's why I'd recommend lowering their seeding rates.

Recommendations

In this experiment, we became convinced that all corn hybrids react to variable-rate seeding differently. For that reason, you have to test a hybrid in specific soil and climatic conditions to determine the optimal seeding strategy.

In the agricultural holding's particular soil and climatic conditions, it turned out that the lower the FAO is (below 350), the better the hybrid reacts to variable-rate seeding. In all fields where yield didn't increase, we noticed that it also didn't change when decreasing the seeding rate. This could be a basis for decreasing the seeding rate for these hybrids at the agricultural holding.

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Usevalad Henin
Create a seeding map with OneSoil
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